In a substrate processing apparatus that executes a specific type of processing such as etching or film formation on a substrate which may be a semiconductor wafer or a glass substrate, the substrate having been carried into a processing chamber and placed on a stage via a transfer arm or the like undergoes processing such as etching while it is vacuum-held onto the stage. Once the processing is completed, the substrate is detached from the stage by, for instance, pushing up a lift pin disposed so as to be allowed to move up/down freely, and is carried out via the transfer arm or the like.
An electrostatic chuck that holds the substrate with an electrostatic force such as the coulomb force as a DC voltage is applied to an electrode plate embedded in, for instance, a dielectric member, is often used as a jig for holding fast the substrate onto the stage. Some electrical charge may remain in the substrate even when the voltage to the electrostatic check holding the substrate is turned off upon completion of the processing and, in such a case, the electrostatic chuck may retain the holding force. As the substrate is detached from the stage via a lift pin or the like in this state, the substrate may become cracked and thus damaged or it may become misaligned. For this reason, processing for electrically discharging the substrate is executed before detaching the substrate so as to reduce the electrostatic holding force (see, for instance, Japanese Laid Open Patent Publication No. H09-064021 and Japanese Laid Open Patent Publication No. H11-274141).
When executing such electrical discharge processing, electrical discharge conditions are set by reading out parameters indicating the electrical discharge conditions (e.g., the voltage to be applied to the electrostatic chuck, the processing chamber internal pressure and the flow rate of the gas to be drawn into the processing chamber) stored in advance together with the substrate processing conditions (processing recipe), and the electrical discharge processing is executed based upon the electrical discharge conditions thus set.
However, since the values of the individual parameters indicating the electrical discharge conditions stored in advance are set on the assumption that the substrate is to be electrically discharged upon a normal completion of the processing on the substrate, the substrate is not always electrically discharged to the full extent, depending upon the state of the substrate undergoing the electrical discharge processing.
For instance, if an abnormal condition occurs in the substrate processing apparatus while the processing on the substrate such as etching is in progress and thus the processing does not end normally, the substrate may become held onto the stage with excessive force, depending upon the cause of the abnormal condition or the length of time over which it is left untended. In such a case, the substrate may not be electrically discharged to the full extent by executing the electrical discharge processing under the electrical discharge conditions stored in advance, to result in cracking or misalignment of the substrate.